Add random to Bool, including a test

[MaxHaertwig]

Checklist

• I checked the Contributing Guidelines before creating this request.
• New extensions are written in Swift 4.
• New extensions support iOS 8.0+ / tvOS 9.0+ / macOS 10.10+ / watchOS 2.0+.
• I have added tests for new extensions, and they passed.
• All extensions have a clear comments explaining their functionality, all parameters and return type in English.
• All extensions are declared as public.

I'm not quite sure about the test, but the chance that it fails should be sufficiently small.

[SwifterSwiftBot]

	2 Warnings
⚠️	Consider adding tests for new extensions or updating existing tests for a modified SwifterSwift extension
⚠️	The source files have been modified. Please consider adding a CHANGELOG entry if necessary.

	1 Message
📖	Thank you for submitting a pull request to SwifterSwift. The team will review your submission as soon as possible.

Generated by 🚫 Danger

[codecov]

Codecov Report

Merging #272 into master will increase coverage by 0.1%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master     #272     +/-   ##
=========================================
+ Coverage   54.86%   54.96%   +0.1%     
=========================================
  Files          46       46             
  Lines        3292     3300      +8     
=========================================
+ Hits         1806     1814      +8     
  Misses       1486     1486

Impacted Files	Coverage Δ
Tests/SwiftStdlibTests/BoolExtensionsTests.swift	100% <100%> (ø)	⬆️

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[SD10]

It would be nice to not do this 10,000 times 😱 Just making note of it

[omaralbeik]

@SD10 I agree, 10 times is enough, will update it soon